The preliminary evaluation of the juvenile period (nursery stage and one year after planting) is now possible, permitting the study of the behaviour of different origins 10 years after the seedling (Nasrallah and Khélifi, 2010).
2.1. Effect of the station
Survival and plant height measurements taken one month after planting (winter 2007) did not reveal significant differences between the two sites. However, the measurements taken nine years later were significant. The Newman-Keuls tests show that the green oak origins reacted differently to the environmental conditions.
Plant survival was higher at the Sidi Benkadour site (46%) compared to the Sidi Moussa (31%) plantation site. The pedoclimatic conditions of the first site seem to be more suitable for these 21 green oak origins than those of the second site (Table 3). We noted also that many plants rated dead (either due to a lack of water or grazing by wildlife) were able to resume again as a result of improved weather conditions. The plant height growth at the first site was 132.10 cm compared to the second site, which was 113.80 cm.
The differences in survival and total heights recorded in the two plantations, 10 years after planting, explain the significant differences in biomass production and carbon sequestration between the two sites (Table 4). The 21 green oak provenances were better expressed at the first site, producing 417.87g of total fresh biomass (TFB) and 159.26 g of carbon, compared to the second site, which produced 402.04 g of TFB and 144.09 g of carbon.
The average amount of atmospheric carbon sequestered at the first site was 0.2987 t CO2 /ha compared to 0.1820 t of CO2 /ha at the second site. The amount of CO2 sequestered in the first plantation was 2.54 t of CO2, compared to 1.55 t of CO2 in the second one.
The average production of fresh biomass was 0.2136 t/ha at the Sidi Benkadour site, compared to only 0.1385 t/ha at the Sidi Moussa site. A total fresh biomass production of 1.82 t/ha was obtained at the first site, compared to 1.18 t/ha at the second site.
2.2. Inter-provenance variability
2.2.1. Evolution of plant survival and total height plants
The variance analysis of survival criteria, which was done one month after planting, had no significant effect on either the sites or provenances. Both sites recorded very low mortality (0.01%). This result shows that transplant shock was prevented (Nasrallah, 2014).
Measurements taken at the end of autumn 2016 in both sites recorded the survival of 38.5% of the plants. Survival varied significantly (at the threshold of α= 0.05%) between sites and within the sites themselves, but without interaction between site and origin. Based on analysis of the Newman–Keuls tests, origins were divided into six homogeneous groups (HG) in the first site and seven HG in the second one (see Table 3):
- At the site of Sidi Benkadour (1), the origin of Boualem, belonging to the ecological group of the Saharan Atlas, had the highest survival rate (57%), whereas the provenance of Sour Ghozlane of the fourth ecological group had the lowest survival rate (29%).
- At the Sidi Moussa site (2), the dar Echioukh origin survival rate was 40% in comparison to 20% for of Oued Yesser origin.
- The provenances of Saharan Atlas group responded better to the conditions of the plantations of the sites. However, provenances of the northern side of the Tellian Atlas, and to a lesser extent those of its southern side, were responded poorly to the conditions of the sites.
The variance analysis done on the total heights of the plants, one month after planting, revealed a significant effect on the provenance (α = 0.05%), but not on the sites. The average total height (ATH) for the entire plantation was 17.28 cm.
Height measurements taken in both plantation sites at the end of autumn 2016 recorded an ATH of 122.95 cm. The ATH of the plants varies significantly (α = 0.05%), between the provenances at each site and between the sites, with the presence of an interaction origins x sites. Analysis of the Newman–Keuls tests put the g provenances of the first site into eight groups, compared to six groups in the second one:
- The Boualem and Jebel Aissa origins from the ecological group of the Saharan Atlas are distinguished by a larger ATH of 157.65 cm and 139.26 cm in the first and second site, respectively. The best second origin is reserved to Zaccar (139.30cm).
- The ATH of origins of Guelma were 121.27 cm in the first site and 98.36, 99.64 and 102.58 cm for Bordj Bounaama, Oued Yesser and Belezma provenances, respectively, at the second plantation site.
- The green oak origins of the Saharan Atlas ecological group recorded the highest ATH in both sites, while those of the Tellian Atlas showed the lowest ATH at the both sites.
2.2.2. Fresh biomass and carbon sequestration from origins
The average total fresh biomass (TFB) ranged from 1.15g to 5.19 g. The analysis formed 11 homogeneous groups. The highest weights were recorded for the provenances of Zaouet, Bel Abed and Dar Echioukh and the lowest weight was recorded by the provenance of Câbet Lakhra (Nasrallah, 2014). Analysis of the variance (at the threshold of α= 0.05%), TFB of the aerial parts of the plants of the two sites (from seedling until 10 years of age) revealed 1.15 g to 5.19 g.
The analysis formed 11 homogeneous groups. The highest weights were recorded by the provenances of Zaouet, Bel Abed and Dar Echioukh and the lowest weight by Câbet Lakhra (Nasrallah, 2014). Analysis of the variance (at the threshold of α= 0.05%), TFB of the aerial parts of the plants of the two plantation sites (from seedling until 10 years of age) revealed significant differences between the provenances of each site and also between the two sites, with a remarkable interaction between site and provenance.
The Newman–Keuls tests divided the provenances at the first site into nine groups and those at the second site into two groups (Table4). The Zaccar and Jebel Aissa origins from the northern ecological region the Tellian Atlas and the Saharan Atlas groups were characterised by TFB. The TFB production at the first site and second site was 474.22 and 461.79 g, respectively. The TFB production of the provenances from Oued Yesser, Chaâbet Lakhra, Bordj Bounaama, El Bordj, Frenda, Gulema, Sebdou and Mezaouro was low at the first site.
The ecological group of the Saharan Atlas produced the highest TFB average at both sites. The average biomass production of provenance of the northern part of the Tellian Atlas was higher than those of the second site. Nevertheless, the provenances of the second and third ecological groups produced the lowest TFB.
The calculation of TFB in t/ha at Sidi Benkadour showed that the provenances of the Saharan Atlas, followed by those of the inner plains, have the highest production with 0.0110 and 0.0092 t/ha, respectively. The origins of the two slopes of the Tellian Atlas (south and north) have a low TFB/ha value (south: 0.0099 t/ha, north: 0.0079 t/ha). Concerning the Sidi Moussa site, the origin TFB/ha values were not important. The provenances of the Saharan Atlas (0.0068 t/ha) and those of the inner plains (0.0067 t/ha) have better TFB/ha production than the southern (0.0060 t/ha) and the northern (0.0053 t/ha) slopes of the Tellian Atlas.
In the first site, the provenance of the Saharan Atlas and the south of Tellian Atlas sequestered amounts of CO2 above the general average (0.0154 t CO2/ha and 0.0138 t CO2/ha, respectively). Concerning the two others provenances of the southern intern plains of Tellian Atlas ecological zones and the northern part, the quantity of CO2 sequestered was 0.0129 t CO2/ha and 0.0111 t CO2/ha respectively. A lesser amount of CO2 was sequestered at the second site, with higher averages for the Saharan Atlas (0.0090 t CO2/ha) and inner plains (0.0089 t CO2/ha) when compared to those in the southern (0.0078 t CO2/ha) and northern Atlas (0.0071 t CO2/ha) groups.